On the Toptal blog Ilya Sanosyan has a post sharing what he sees as the top ten most common mistakes PHP developers make on a day to day basis. While most of the tips are code-specific there are one or two that are a bit more abstract.

PHP makes it relatively easy to build a web-based system, which is much of the reason for its popularity. But its ease of use notwithstanding, PHP has evolved into quite a sophisticated language, with many nuances and subtleties that can bite developers, leading to hours of hair-pulling debugging. This article highlights ten of the more common mistakes that PHP developers need to beware of.

Among the items on his list are things like:

Leaving dangling array references after foreach loops

Confusion about returning by reference vs. by value

Memory usage headfakes and inefficiencies

Assuming $_POST will always contain your POST data

Thinking that PHP supports a character data type

Each of the items comes with a good description, some code and suggestions on how to avoid and/or fix it in your applications.